Combustion of compressed air and fuel in the cylinders of internal combustion engines adds large amounts of heat to the axially outer areas of the cylinder liner and engine structure surrounding the cylinders. The structures, normally called the head, closing the axially outer end of the cylinder liner normally includes intake and exhaust passages communicating with the combustion chambers. These passages permit the ingress of air to the combustion chamber and egress of hot exhaust gas after combustion of a fuel-air mixture. Intake valves are normally located in the intake passages to control admission of the air to the combustion chamber. Likewise, an exhaust valve is located in the exhaust passage or passages to permit venting of the hot exhaust gas during the scavenge stroke of the piston. Due to the arrangement of the intake and exhaust valves in the structure, the exhaust passage or passages are located adjacent a particular circumferential area of the cylinder liner.
As the hot exhaust gas exits the cylinder through the exhaust passage, the head structure and the circumferential area of the cylinder liner adjacent the exhaust passage absorbs additional energy. This creates what is commonly referred to as a "hot spot", resulting in a considerable temperature gradient circumferentially around the liner. The temperature gradient can result in distortion of the liner, resulting in an imperfect seal with sealing rings carried by the piston, with attendant, undesirable increase in blowby and/or increased oil consumption.
In many instances, the combustion energy propagates to an area of the liner where the axially outer sealing ring of a piston stops when the piston is in its axially outermost position. This establishes what is commonly referred to as a "top ring turn around position" on the cylinder liner. Excessive temperature in the area of the liner can result in coking of oil and sticking of the rings in the mating grooves in the pistons. Sticking of the rings can produce excessive blowby; ie, combustion pressure in the crankcase, and/or excessive oil consumption, as well as possible excessive wear of the rings and cylinder liner.
It is desirable that a cooling system be provided to cool the top ring turn around position area of a cylinder liner to avoid coking of oil in the ring groove and attendant ring sticking. It is also desirable to provide enhanced cooling of cylinder liners in the area of the exhaust ports to achieve a more consistent temperature gradient around the liner to reduce distortion thereof and minimize the resultant problems. Further, it is desirable to cool only those areas of the engine that specifically need cooling to avoid other thermal gradients and lessen the heat load on the heat exchangers.
The present invention is directed at overcoming the problems as set forth above.